Electromagnetic device



C. W. BURROWS.

ELECTROMAGNETIC DEVKCE.

APPLICATION FILED APR-27,1917.

Patented May 18, 1920.

FIG. 1

"tlllllll has INVENTOR UNITED STATES PATENT QFFTQE.

CHARLES W. BURROWS, OF WASHINGTON, DISTRICT OF COLUMBIA.

ELECTROMAGNETIC DEVICE.

Application filed April 27,

To all whom it may concern Be it known that 1, CHARLES W. Bmmows, a citizen of the United States, residing in the city of Washington, District of Columbia, have invented certain new and useful Tmprovements in Electromagnetic Devices, of which the following is a specification.

My invention relates to electromagnets.

I will describe one form of electromagnet embodying my invention and will then point out the novel features thereof in claims.

In the accompanying drawings, Figure 1 is a view showing in front elevation one form of electromagnet embodying my invention. Fig. 2 is a view showing in end elevation the electromagnet shown in Fig. 1. Fig. 3 is a transverse sectional view taken on the line TIL-III of Fig. 1 looking in the direction of the arrows.

Similar reference characters refer to similar parts in each of the several views.

Referrin to the drawings in detail, the electromagnet comprises in this instance two cores designated C and C, respectively, each being formed of magnetizable material, usually soft iron, and preferably circular in cross-section. Each core is provided with enlarged end flanges P, P of magnetizable material, also usually of soft iron, which flanges are preferably, though not necessarily, integral with the body of the core. Each core, therefore, constitutes in itself a spool on which a wire coil V may be wound, and the lower-flange P of each core also constitutes the pole-piece for such core.

Each core with its flanges is preferably provided with a coating of enamel to insulate the winding from the iron, thus providing an insulation of minimum thickness and so bringing the wire as close as practicable to the iron. The entire core with its flanges may be dipped in the enamel, and the enamel may then be removed from the outer ends of the flanges. The enamelv remaining on the edges of the flanges prevents rusting and also assists in avoiding electric surface leakage.

As here shown, the cores G and C are arranged in parallel spaced relation and are rigidly connected at their upper ends by a back strap B and at their lower ends by a strip S. The back strap B is formed of magnetizable material, usually soft iron, and is secured to the upper ends of the cores by screws E, E. The back strap is of such size and contour that it engages with the Specification of Letters Patent. Patented lay 18 1920 1917. Serial No. 164,892.

flanges P, P through their entire area, thus giving a large area of contact between the cores and the back strap and so reducing to a minimum the magnetic reluctance of this part of the magnetic circuit. To further decrease the reluctance of this part of the circuit, the flanges P, P may be arran ed in mutual contact, as shown. The strip connecting the pole-piece flanges P and P is formed of non-magnetizable material, such brass, and as here shown is secured to the rear edges of the flanges P, P by screws F. The length of strip S is such that it projects beyond the outer edges of the flanges. Each projecting end of the strip S is provided with a bracket L secured to the strip by screws K, K, a portion of the bracket depending from the strip and being provided with a threaded orifice to receive a bearing screw it. The inner ends of the bearing screws R, R- constitute pintles for pivotally supporting an armature A.

The rear edge of the armature A is provided with ears D, D in which the pintles R, are journaled. it will be seen, there .0. fore, that the pivotal points of the armature are laterally displaced from the polepieces, and that there is practically no part of the armature back of the axial line of the pivotal points. Consequently, the torque around the pivotal axis exerted on the armature by the magnet is all in the same direction, and no back torque can exist to retard the movement of the armature.

, It will be noted from the drawing that the armature A overhangs the pole-pieces P, P on all sides except the back. The purpose of this construction is to cause as much as possible of the magnetic flux from the pole-pieces to pass through the armature and so to utilise to the highest possible degree the flu created by current in the windings TV, N.

The flanges P and P are preferably rectangular, as shown, thus providing the greatest possible area for engagement with the back strap and for cooperation with the armature, and so assisting to reduce the reluctance of the magnetic circuit. I have also found that the flanges P, P constituting the pole-pieces of the magnet, may advantageously be dis-symmetrical with respect to the core body; that is, that these flanges may be extended in one direction or the other from the center of the core body in the gen eral direction of the plane of the two core bodies. The exact amount of such dis-symmetry must be determined in each case by experiment.

The strip S, as here shown, is provided at its medial portion with an arm V formed of non-magnetizable material and arranged between the pole pieces P, P, which arm maintains the 'cores C and C in parallel spaced relation. The free end of the arm V projects beyond the edges of the pole pieces and is provided with a screw T adjustably mounted therein, such screw being locked in any adjusted position by means of a nut t. This screw T is provided for the purpose of determining the attracted position of the armature A, it being understood that by adjusting the screw within the arm V the attracted position of the armature is accordingly varied to cause the proper amount of torque to be exerted on the armature.

From the foregoing description, taken in conjunction with the accompanying draw ings, it will be manifest that have provided an electromagnet having a particularly high degree of efficiency.

Although I have herein shown and described only one form of electromagnet embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the ap pended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. An electromagnet comprising two magnetizable cores each provided with integrally formed end flanges, a back strap bridging said cores at one end, a coil surrounding each core between its flanges, a non-magnetizable strip connecting the other ends of said cores and having a portion thereof disposed between the flanges at such ends, to maintain such flanges in proper spaced relation, and an armature pivotally mounted on said strip.

2. An electromagnet comprising two magnetizable cores each provided with enlarged magnetizable end flanges, a back strap con necting said cores at one end, a coil surrounding each core between its flanges, a non-magnetizable strip connecting the other ends of said cores and having a portion thereof disposed between the adjacent flanges, an armature pivotally mounted on said strip and means mounted on said strip for adjusting the closed position of said armature.

3. An electromagnet comprising two cores each provided with'a pole-piece and an armature located opposite the faces of said pole-pieces and mounted to swing 011 an axis substantially opposite one of the edges of said pole-pieces, all edges of the armature except the pivotal edge overhanging the corresponding edges of the pole-pieces.

4. An electromagnet comprising two parallel cores, each core having an enlarged flange at each end and both flanges on each core being integral with the body of the core, the two flanges at one end constituting the polepieces of the electromagnet, and a back strap of niagnetizable vmaterial connecting the other two flanges and contacting therewith throughout substantially the entire area of each flange.

5. An electromagnet comprising a pair of magnetizable spools, coils on said spools, a magnetizable member bridging said spools at one end, a non-magnetizable member connecting said spools at the other end, and an armature pivoted to said non-magnetizable member, the pivot point of said armature being located laterally with respect to said spools for the purpose described.

6. An electromagnet comprising two magnetizable cores each provided with an enlarged magnetizable end flange integral with the core, at least one edge of each flange being straight and the straight edges of the two flanges being in mutual contact, and a magnetizable back strap contacting with each flange throughout substantially the entire area of the flange.

7. An electromagnet comprising. a pair of magnetizable cores each provided with an enlarged magnetizable end flange, and a magnetizable back strap connecting said cores and contacting with each end flange throughout substantially the entire area of the flange.

In testimony whereof I aflix my signature in presence of two Witnesses.

CHARLES W. JBURROWS. lVitnesses S. M. THRIFT. HERBERT SMITH. 

